class Counter(object):
    def __init__(self, init=0, step=1):
        self. __counter = init
        self.__step = step

    @property
    def step(self):
        return self.__step
    @property
    def current(self) -> int:
        return self.__counter

    def increase(self) -> int:
        self.__counter += self.step
        return self.__counter

    def decrease(self) -> int:
        self.__counter -= self.step
        return self.__counter

    def __str__(self):
        return "counter:{},step:{}".format(self.__counter, self.__step)

import unittest
class TestCounter(unittest.TestCase):
    def test_main(self):
        c = Counter()
        self.assertEqual(0, c.current)
        self.assertEqual(1, c.step)

        c.increase()
        self.assertEqual(1, c.current)
        c.decrease()
        self.assertEqual(0, c.current)

